The objective of this proposal is to delineate the molecular mechanisms by which a diet rich in omega 3 fatty acids (w 3FAs) is injurious to the liver. Because the hepatic injury induced by fish oil may be exacerbated by the concomitant use of another hepatotoxin, such as alcohol, both agents will be employed to determine whether fibrogenesis is enhanced. Specific Aims: 1) to determine the level of gene regulation by which w 3FAs alone, and in combination with ethanol, initiate hepatic fibrogenesis; 2) to analyze the actions of a diet rich in w3FAs and ethanol on the formation of eicosanoids. 3) to ascertain the effects of w3FAs and ethanol administration on fibrogenic cytokine synthesis; 4) To determine whether the molecular mechanisms by which w3FAs and ethanol induce liver injury differ from the mechanisms of CCl4-induced fibrosis; and 5) to delineate the antifibrogenic effects of specific biological agents. Methods: Rats will be fed a diet rich in w3FAs or rich in saturated fats +/- ethanol for six months. Livers will be evaluated for collagen and other extracellular matrix gene expression by light and electron microscopy, HPLC analysis, Northern blot hybridization studies, and nuclear run-on assays. Eicosanoid analysis of liver tissue will be accomplished by HPLC and RIA. The cascade of inflammatory and fibrogenic cytokines will be investigated by biological assays and determination of steady state mRNA levels and gene transcription rates. The gel retardation assay and DNase I footprinting will be used to assess differences in nuclear-binding proteins that may exist between CCl4 - induced fibrosis and injury induced by w3FAs and ethanol administration. Biological agents such as PGE2, gamma-interferon, and neutralizing antibodies to TGF beta or TNF alpha will be used to intervene in the fibrogenic process. In vitro studies of hepatocytes, Ito cells, and Kupffer cells will also evaluate the effects of w3FAs and ethanol on matrix formation, eicosanoid metabolism, and cytokine production. Health relatedness: The hypothesis that w3FAs may play a role in hepatic fibrogenesis is a novel concept with important therapeutic implications; if shown to be true, this theory would raise serious questions about the indiscriminate use of w3FAs.